# Resistor question for 5 volt 92 mA small stepper motor used with arduino.

#### Calum Workman

Joined Oct 10, 2015
3
I'm fairly new to arduino and I'm trying to get a stepper motor to turn according to a potentiometer. I have to use an external power source with 2 amps because my arduino only has one 5 volt plug, which i'm using for my potentiometer. according to an online calculator, i need a 55+ ohm resistor with .47+ watts. 75% of the resistors I saw on eBay were .25 watts, and according to some other threads 99% of arduino tasks don't need more than .25 watts, so i'm assuming a small stepper motor doesn't exceed this. I skimmed through a 400 page arduino guide, and it didn't mention resistor wattages once, so first off does it matter if i use a .25 watt resistor for a .5 watt task, and second off is my maths/online calculator right? Third off, the piece of code I'm using gave a note that my motor would draw 97 mA(i'm definitely using the same motor as they were talking about). http://www.numbatconspiracy.com/moodle/course/view.php?id=134 Press control + f then type stepper motors to find the task. Is it right saying that the motor will draw 92 mA?
I'd really appreciate some assistance with this, because I'm quite new to circuits. Thank you in advance!

#### MikeML

Joined Oct 2, 2009
5,444
I have never seen a stepping motor that operates on such a low current. More likely, it requires ~1A per winding.

Do you have any data on the stepping motor, specs, maker, model? Post a picture of the markings on it.

How many wires does the stepper have?

Can you measure the resistance of the windings with an Ohmmeter?

Did you buy the L298N Stepper Drive PC board with it?

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#### Calum Workman

Joined Oct 10, 2015
3
I'm using a 28byj-48 stepper motor.

On the other side of the stepper motor it says 5 volts DC. I'm using an external power source rather than the arduino. The green board in there is my stepper motor driver. I don't own an ohmmeter, so I can't do that. I found a site giving some specs of the motor, but they are different to the ones I found in the code notes. https://arduino-info.wikispaces.com/SmallSteppers
Really appreciate the help!

#### shteii01

Joined Feb 19, 2010
4,644
I found a site giving some specs of the motor, but they are different to the ones I found in the code notes. https://arduino-info.wikispaces.com/SmallSteppers
Really appreciate the help!
Then this is waste of everyone's time.

Normal people first collect and compile the information about their parts, then they order the parts, then they build "stuff".

You seem to go at it the other way. You got the parts, you build "stuff". And now you are trying to figure out how to make the parts work.